Tobit Curteis, wall paintings conservator and specialist in
environmental control at historic sites, outlines his recent work at
Royston Cave

Excerpt from Cornerstone magazine, Issue 1, 2010

Over the course of the past 50 years numerous attempts have been
made to understand the deterioration and to repair the damaged
carvings. However, most studies have ended prematurely and only limited
remedial measures have been implemented. In 2008, a detailed study of
the Cave was commissioned by the Royston Town Council and supported by
a generous grant and specialist advice from English Heritage, with the
aim of understanding how and why the Cave is deteriorating, so that
measures to conserve it could be developed.

It immediately became apparent that the causes of deterioration are
as unusual as the Cave itself. Because it is carved in soft, Upper
Cretaceous chalk, (rather than the harder, older beds) very little
research has been done on the precise decay mechanisms or their
control. To add to this, there is relatively little research in the UK
on the deterioration of this type of cave structure. Therefore, the
project, which will take a number of years to complete, involves basic
materials research, as well as the latest digital survey techniques
more commonly associated with historic building conservation.

The preliminary results have demonstrated that the primary cause of
deterioration appears to be minor dimensional change of the chalk, as a
result of fluctuations in the moisture content, resulting largely from
periodic flooding, but also due to changes in the microclimate. This
leads to internal stresses which cause fine cracks to occur, often in
the vertical plane between the raised carved detail and the main face
of the Cave. The fissures are then colonised by microbiological growth
and animals, causing the cracks to enlarge and eventually these
sections of carving to fall away. Historically, this may have been
exacerbated by traffic vibration, although since the opening of the
nearby bypass in the 1980s, this is likely to have been substantially
reduced.

In conjunction, damage has been caused to the chalk by worms, which
appear to feed on nutrients which have entered as a result of flooding
with fowl water. The effect of the worm activity is to cause a loss of
cohesion and collapse of certain sections of a softer chalk and a
consequent loss of the carved detail.

With the basic decay mechanisms now apparent, both preventive and
interventitive conservation approaches are being evaluated. As with all
sensitive historic structures, the primary aim is to control the
deterioration mechanisms and, therefore, minimise the level of
treatment that needs to be applied. Given the unusual nature of the
structure and the limited reversibility of treatments, an extremely
cautious approach is being adopted, and the conservation process will
be slow and painstaking. Indeed, the real conservation process will be
open ended as, once the current phase of damage is stabilised, the long
term survival of the Cave depends on preventing future deterioration,
rather than treating it once it has occurred.

Royston Cave is managed by the Royston & District Local History Society on behalf of Royston Town Council.